Gas turbine engines may be used to power various types of vehicles and systems, such as air or land-based vehicles. In typical gas turbine engines, compressed air generated by axial and/or radial compressors is mixed with fuel and burned, and the expanding hot combustion gases are directed along a flowpath and through a turbine nozzle having stationary turbine vanes. The gas flow deflects off of the vanes and impinges upon blades of a turbine rotor. A rotatable turbine disk or wheel, from which the turbine blades extend, spins at high speeds to produce power. Gas turbine engines used in aircraft use the gas turbine aft end to produce a forward thrust. Other gas turbine engines may use the power to turn a propeller or an electrical generator.
One way to increase cycle efficiency of a gas turbine is to operate at higher turbine inlet temperature (TIT). In most engines, the turbine inlet temperatures have increased well above the metallurgical limit of engine components. Film cooling of gas turbine components (blades and vanes) is a widely used technique that allows higher turbine inlet temperatures by maintaining material temperatures within acceptable limits. With film cooling, air is extracted from the compressor and forced through internal cooling passages within turbine blades and vanes before being ejected through discrete film cooling holes onto the external wall surfaces of the airfoil. The cooling air leaving these film cooling holes forms a film layer of cooling air on the component surface which protects the component from hot gas exiting the combustor by substantially reducing heat transfer from the hot gas to the blade skin as the cooling air is at a lower temperature than the hot gas. Although the aforementioned film cooling systems operate adequately, they may be improved. For example, in the airfoil leading edge region, at lower blowing ratios, the cooling air (also known herein as “coolant”) can get carried away by the accelerating mainstream flow of hot gas due to lower coolant radial momentum. At higher blowing ratios, the cooling film may blow-off from the leading edge external wall surface, both scenarios substantially impeding formation of the film layer of cooling air against the airfoil external wall surface, resulting in lower cooling effectiveness.
Accordingly, it is desirable to provide improved film cooled components such as turbine blade airfoils, film cooling systems, and methods for forming an improved film cooled component, such as the airfoil of a turbine blade. The improved film cooling systems may effectively cool components that are typically subjected to elevated operating temperatures, such as those above about 1100° C. In addition, it is desirable for the film cooling systems to provide better film cooling. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.